Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. For example, it is known to use such systems to treat neurological disorders, such as neurodegenerative diseases (e.g., Alzheimer's Disease, Parkinson's Disease, tremor, and epilepsy), brain ischemia, such as stroke, and limbic disorders, as well as non-neurological disorders, such as migraine headaches, obesity, and incontinence, by electrically stimulating selected portions of the brain. In a deep brain stimulation (DBS) procedure, typically used to treat Parkinson's Disease, Tremor, and Epilepsy, a selected deep brain structure, e.g., the anterior thalamus, ventrolateral thalamus (Thal), internal segment of globus pallidus (GPi), substantia nigra pars reticulata (SNr), subthalamic nucleus (STN), external segment of globus pallidus (GPe), and neostriatum, is electrically stimulated. Further details discussing the treatment of diseases using DBS are disclosed in U.S. Pat. Nos. 6,845,267, 6,845,267, and 6,950,707, which are expressly incorporated herein by reference. In a cortical brain stimulation procedure, typically used to rehabilitate stroke victims, but also providing benefits in the treatment of the other aforementioned disorders, the cortical brain tissue underneath the dura mater is electrically stimulated.
A typical implantable neurostimulation system used to electrically stimulate brain tissue includes electrodes, which are implanted at the desired stimulation site in the brain of the patient, and a neurostimulator implanted remotely from the stimulation site (e.g., in the chest region of the patient), but coupled either directly to the electrodes via one or more leads. The neurostimulation system may further comprise a handheld remote control (RC) to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. The RC may, itself, be programmed by a technician attending the patient, for example, by using a Clinician's Programmer (CP), which typically includes a general purpose computer, such as a laptop, with a programming software package installed thereon.
Thus, in accordance with the stimulation parameters programmed by the RC and/or CP, electrical pulses can be delivered from the neurostimulator to the electrodes to stimulate or activate a volume of tissue and provide the desired efficacious therapy to the patient. The best stimulus parameter set will typically be one that delivers stimulation energy to the volume of tissue to be stimulated in order to provide the therapeutic benefit (e.g., treatment of movement disorders), while minimizing the volume of non-target tissue that is stimulated. A typical stimulation parameter set may include the electrodes that are acting as anodes or cathodes, as well as the amplitude, duration, and rate of the stimulation pulses.
When the neurostimulation system is implanted within a patient, a fitting procedure is typically performed to ensure that the stimulation leads and/or electrodes are properly implanted in effective locations of the patient, as well as to program the neurostimulator by selecting one or more effective sets of stimulation parameters that result in optimal treatment for the patient and/or optimal use of the stimulation resources. Notably, the persons that program the neurostimulators are often trained by experience alone, and lack formal training in the theory of neurostimulation. Thus, obtaining an optimal program is difficult and sometimes not achieved, resulting in a fitting process that is extremely time consuming and tedious.
Significantly, non-optimal electrode placement and stimulation parameter selections may result in excessive energy consumption due to stimulation that is set at too high an amplitude, too wide a pulse duration, or too fast a frequency; inadequate or marginalized treatment due to stimulation that is set at too low an amplitude, too narrow a pulse duration, or too slow a frequency; or stimulation of neighboring cell populations that may result in undesirable side effects. In addition, the brain is dynamic (e.g., due to disease progression, motor re-learning, or other changes), and a program (i.e., a set of stimulation parameters) that is useful for a period of time may not maintain its effectiveness and/or the expectations of the patient may increase. Thus, after the neurostimulation system has been implanted and fitted, the patient may have to schedule another visit to the physician in order to adjust the stimulation parameters of the neurostimulator if the treatment provided by the system is no longer effective or otherwise is not therapeutically or operationally optimum. All of these issues are poorly addressed by the present-day neurostimulation fitting techniques.
While neurostimulation systems have been disclosed that utilize a closed-loop method that involves sensing electrical signals within the brain of the patient and adjusting the electrical stimulation delivered to a target region within the brain of the patient (see, e.g., U.S. Pat. Nos. 5,683,422 and 6,016,449), the physician must still physically adjust the stimulation lead position in order to locate the locus of the delivered stimulation energy at the proper tissue site, and thereby achieve optimum, or otherwise effective, therapy. In addition, if the therapy provided by the implanted neurostimulation system no longer is optimum or effective, the patient may need to undergo another surgical procedure to adjust the physical position of the stimulation lead. Furthermore, it is often the case, either due to the dysfunction suffered by the patient or for other reasons, that the patient may have difficulty operating the RC to adjust the stimulation parameters to maintain optimum or effective treatment.
There, thus, remains a need for a neurostimulation system that can be more easily programmed to adjust the position of the locus of stimulation energy delivered by the system to brain tissue in order to optimize treatment of a patient suffering from a disease.